While in Europe on a work trip and grabbing a bite for lunch at a café, I grabbed a bottle of water on my way to pay without checking the label. Checking the label is important, because in Europe, "still" water and "sparkling" (carbonated) water are sold side by side—and I can't stand the taste of sparkling water. Halfway through eating lunch, I opened the water bottle to have a drink and it sprayed water all over my tray and my clothes.

I'd grabbed the wrong sort of water. Not only that, I'd obviously shaken it at some point.

Because I'd opened it, I couldn't return it for a bottle of still water, so I decided to de-sparkle the sparkling water, in the hopes that it would improve the taste. Fortunately, this requires no special equipment and can be done in a café, although it might draw some funny looks.

While we usually calculate reaction rates based on the concentrations found in the bulk solution, in a case of a surface reaction, that's out where no reaction is happening! The equations for reaction rates empirically account for this in the constants, where the reaction rate is rolled together with the rate the reagents diffuse toward the surface to react and the rate the reaction products diffuse away from the surface and out of the way.

But in terms of designing a reaction, controlling it to get, say, the product we want instead of a byproduct if there are two possible reactions, or speeding it up or slowing it down, what happens at the surface can be key. And whether we watch or measure, knowing what happens at the surface is the first step toward changing what happens at the surface.